🚀 go-pugleaf

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1207 PM CST SAT DEC 15 2012

DISCUSSION...

327 AM...MULTIPLE FORECAST CONCERNS/CHALLENGES THROUGH THE PERIOD
THIS MORNING INCLUDING THE POTENTIAL FOR A STRONG WINTER STORM TO
AFFECT THE REGION NEXT THURSDAY.

FIRST UP HOWEVER IS LOW PRESSURE OVER THE PLAINS WHICH WILL MOVE
NORTHEAST TO THE WESTERN LAKES REGION BY SUNDAY MORNING AND THEN
SLOW/STALL OVER THE NORTHERN LAKES INTO MONDAY. FIRST WAVE OF RAIN/
SHOWERS NOW PUSHING NORTH INTO SOUTHWEST WI AFTER MOVING ACROSS
THE FAR WESTERN CWA EARLY THIS MORNING. MAIN BAND OF RAIN TO
AFFECT THE AREA ASSOCIATED WITH CORRIDOR OF BETTER LIFT EXTENDS
FROM SOUTHERN IA CURVING SOUTHEAST INTO SOUTHERN IL. BEST LIFT
HOWEVER LOOKS LIKE IT MAY END UP SPLITTING NORTHERN IL WITH RAIN
AMOUNTS POSSIBLY VARYING WIDELY. QUITE A BIT OF LIGHTNING EAST OF
THE LOW FRIDAY EVENING BUT VERY LITTLE DETECTED IN THE PAST FEW
HRS. BEST CHANCE OF THUNDER STILL WITH THE BETTER LIFT/BEST
INSTABILITY ALOFT WHICH WOULD BE FROM MID/LATE MORNING THROUGH
EARLY AFTERNOON AND STILL WORTHY OF CONTINUED SLIGHT CHANCE
MENTION. A WEAKER WAVE THEN MOVES ACROSS THE AREA LATER THIS
AFTERNOON INTO THIS EVENING AND MAY GENERATE ADDITIONAL SHOWERS.

LOW TEMPS FRIDAY EVENING HAVE RISEN A FEW DEGREES OVERNIGHT BUT
DRIER AIR STILL ADVECTING IN FROM THE SOUTHEAST AND WILL TAKE SOME
TIME BEFORE LOW LEVEL MOISTURE PUMPS DEWPOINTS INTO THE 40S LATER
THIS MORNING SO COULD STILL SEE TEMPS FALL A FEW DEGREES BEFORE
SUNRISE...MAINLY EASTERN AREAS. SOUTHEAST FLOW WILL LIKELY KEEP
THE IL SHORE A FEW DEGREES COOLER...SIMILAR TO FRIDAY. OTHERWISE
EXPECT HIGHS TO RANGE FROM UPPER 40S NORTH TO PERHAPS MID 50S
SOUTH...THOUGH CONFIDENCE ON JUST HOW HIGH TEMPS WILL GO IS ONLY
MEDIUM GIVEN CLOUD COVER/PRECIP. ANY BREAKS IN THE CLOUDS COULD
EASILY ADD ANOTHER 2-4 DEGREES TO THE EXPECTED HIGHS. AS WINDS
SHIFT MORE SOUTHWESTERLY LATE AFTERNOON OR EARLY THIS EVENING...
EXPECT TEMPS TO WARM...PERHAPS SEVERAL DEGREES...ALONG THE IL
SHORE.

WITH LITTLE CHANGE TO THE AIRMASS AND DEWPOINTS WELL INTO THE
40S...EXPECT TEMPS TO SLOWLY FALL THIS EVENING AND MAY END UP
BEING TOO COOL. BUT A WEAK COLD FRONT MAY SAG INTO NORTHWEST IL
BY MORNING WHICH SLOWS AS ANOTHER WEAK LOW DEVELOPS ALONG THE
FRONT OVER THE SOUTHERN PLAINS SUNDAY. THIS WILL LIKELY SLOW THE
FRONT ENOUGH FOR SOUTHWEST FLOW TO AID TEMPS REBOUNDING BACK INTO
THE UPPER 40S ACROSS THE CENTRAL PART OF THE CWA AND INTO THE
LOWER 50S FOR AREAS SOUTH OF A GYY/PNT LINE SUNDAY AND WITH ANY
POSSIBLE BREAKS IN THE CLOUDS...ESPECIALLY ACROSS THE SOUTH...
THESE TOO COULD BE TOO COOL. FOG ALSO A CONCERN OVERNIGHT INTO
SUNDAY MORNING BUT DON/T HAVE VERY HIGH CONFIDENCE OF NOT ONLY IT
OCCURRING BUT ALSO WHERE AND TO WHAT EXTENT. DO THINK THERE WILL
BE QUITE A BIT OF MIST/HAZE WITH VIS 3-5SM POSSIBLE BUT STILL NO
MENTION AT THIS TIME.

APPEARED 24 HRS AGO THAT THERE WOULD BE SOME SHOWERS ALONG AND
BEHIND THE COLD FRONT SUNDAY AFTERNOON AND THAT STILL LOOKS
POSSIBLE BUT CONFIDENCE IS DECREASING REGARDING THEIR POSSIBLE
COVERAGE/INTENSITY GIVEN LACK OF FORCING. CONTINUED MENTION BUT
THIS MAY END UP BEING REDUCED OR REMOVED WITH LATER FORECASTS.
POSSIBLE FOR FALLING TEMPS SUNDAY AFTERNOON...THOUGH DROP LOOKS
RATHER MODEST WITHOUT SIGNIFICANT COLDER AIR BEHIND THE FRONT.

LOW NOTED ABOVE THAT DEVELOPS OVER THE SOUTHERN PLAINS SUNDAY
LIFTS NORTHEAST ACROSS THE OHIO VALLEY ON MONDAY AND CLOSE ENOUGH
THAT PRECIP SHIELD MAY BRING SOME RAIN SHOWERS TO THE AREA AND
DEPENDING ON THE EXTENT OF COLDER AIR...PERHAPS SOME RAIN/SNOW
MIXED. ANY LINGERING PRECIP INTO MONDAY NIGHT WOULD LIKELY FALL
AS MAINLY SNOW AS THE COLUMN IS SUFFICIENTLY COLD BY THAT TIME.
DOESN/T LOOK LIKE ANYTHING SIGNIFICANT BUT THE LOW WILL CONTINUE
TO DEEPEN MONDAY NIGHT AS IT ABSORBS THE LOW STILL OVER THE
NORTHERN LAKES SO WILL NEED TO CONTINUE TO MONITOR THIS SYSTEM. IF
ANY SNOW ACCUMULATION WERE TO MATERIALIZE...APPEARS IT WOULD BE
MINOR AND OVER THE SOUTHEASTERN HALF/THIRD OR SO.

ANOTHER FAST MOVING LOW ARRIVES ON TUESDAY AND THIS HAS BEEN A
SOMEWHAT CONSISTENT FEATURE OVER THE PAST FEW RUNS FROM THE ECMWF.
CURRENTLY HAVE A DRY FORECAST GOING WITH LOW CONFIDENCE EITHER FOR
DRY WEATHER OR PRECIP ARRIVING WITH THIS LOW AND THIS TIME PERIOD
WILL ALSO NEED TO BE MONITORED TO INCLUDED POPS WITH LATER
FORECASTS.

BY WEDNESDAY AFTERNOON...LOW PRESSURE WILL BE DEVELOPING OVER THE
SOUTHERN PLAINS AS AN UPPER LEVEL TROUGH DIGS ACROSS THE MID
SECTION OF THE COUNTRY. WHILE SPECIFICS AND TIMING STILL VARY...
ECMWF AND GFS ARE IN FAIR AGREEMENT FROM THIS DISTANCE WITH A
DEEPENING STORM MOVING NORTHEAST ACROSS OR NEAR NORTHERN IL BY
THURSDAY AFTERNOON AND TO NEAR DETROIT FRIDAY MORNING. EXACT
TRACK WILL OBVIOUSLY HAVE MAJOR IMPACTS ON THE SPECIFICS BUT GIVEN
THE CURRENT TRENDS...LOOKS LIKE THURSDAY MAY END UP BEING FAIRLY
MILD AND WET UNTIL THE LOW PASSES AND PRECIP TRANSITIONS TO SNOW.
OF COURSE A SHIFT OF JUST 50 OR 100 MILES WILL COMPLETELY CHANGE
THE FORECAST. THUS CONFIDENCE IS MEDIUM REGARDING THE STORM... BUT
LOW REGARDING PRECIP TYPE AND TIMING. ONE ADDITIONAL ITEM OF NOTE
IS HOW STRONG THE WIND FIELD COULD END UP BEING WITH THIS STORM
AND IF...OR WHERE...ANY SNOW DOES FALL...WINTER WILL CERTAINLY
ARRIVE/RETURN IN FULL FORCE. CURRENTLY FORECAST SOUNDINGS SUPPORT
GUSTS 35-40 KNOTS AT THE SURFACE WHICH WOULD CAUSE PROBLEMS
REGARDLESS OF PRECIP TYPE. CMS

&&

AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* IFR CIGS DEVELOPING...PATCHY MVFR VSBYS.

* AREAS OF RA BECOMING PATCHY DZ.

* SOUTH WINDS ARND 10 KT WITH GUSTS UP TO 20 KT WILL PERSIST THRU
  SUNSET.

BEACHLER

//DISCUSSION...UPDATED 18Z...

LOW PRESSURE CONTINUES TO WEAKEN AS IT LIFTS NORTHEAST ACROSS
NORTH CENTRAL IA. CONSIDERABLE MOISTURE WAS ASSOCIATED WITH THIS
LOW PRESSURE SYSTEM OVER NORTHERN IL/NORTHWEST IN...WITH NUMEROUS
AIRFIELDS INDICATING IFR CIGS AND PATCHY MVFR VSBYS. LLVL FLOW
REMAINS SOUTHERLY...AND WITH A TIGHT GRADIENT OVERHEAD GUSTS UP TO
20 KT HAVE BEEN NOTED ACROSS THE REGION. WITH THE BULK OF THE
MODERATE/HEAVY RAINFALL LIFTING NORTH/NORTHEAST OF THE
TERMINALS...VCSH OR PATCHY DZ WILL FILL IN BEHIND AND COULD LINGER
THRU THE EVENING/OVERNIGHT HOURS. GUIDANCE CONTINUES TO INDICATE
THAT CIGS MAY DIP BELOW 1000FT AGL...POSSIBLY AS LOW AS 600FT AGL
FOR A FEW AIRFIELDS. IT APPEARS SOME DRYING WILL BEGIN TO TAKE
PLACE DURING THE OVERNIGHT HOURS...HOWEVER THE PRECISE TIME THAT
THIS WILL TAKE PLACE REMAINS A CHALLENGE. HAVE OPTED TO HOLD ONTO
THE LOW CIGS A LITTLE LONGER UNTIL ARND DAYBREAK SUN. DRY AIR WILL
STEADILY ADVECT INTO THE AREA FROM THE WEST...WHICH SHOULD HELP
FURTHER ERODE LLVL MOISTURE AND LIFT CIGS TO VFR CONDS ARND MID-
MORNING SUN. WINDS WILL BEGIN TO TURN MORE WESTERLY THROUGHOUT THE
DAY SUN.

BEACHLER


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* HIGH CONFIDENCE IN THE WIND DIR/SPEED/GUSTS FORECAST.

* MEDIUM/HIGH CONFIDENCE IN THE CIGS FORECAST REMAINING IFR THRU
  OVERNIGHT.

* LOW CONFIDENCE IN THE VSBY FORECAST.

* MEDIUM CONFIDENCE IN TIMING OF CIGS RETURNING TO VFR SUN
  MORNING.

BEACHLER

//OUTLOOK FOR ORD/MDW FOR 00Z MONDAY-12Z SATURDAY...UPDATED 12Z...

SUNDAY NIGHT...VFR.

MONDAY...SLGT CHC SHRA. MAINLY VFR.

TUESDAY/WEDNESDAY...VFR.

WEDNESDAY NIGHT/THURSDAY...RAIN CHANGING TO SNOW. IFR POSSIBLE.
BECOMING VERY WINDY.

FRIDAY...GUSTY NORTHWEST WINDS. MVFR CIGS POSSIBLE.

RATZER

&&

MARINE...
212 AM CST

A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR THE IL/IN NEARSHORE
WATERS THROUGH TONIGHT.

DEEP LOW PRESSURE OVER NORTH CENTRAL KANSAS EARLY THIS MORNING WILL
LIFT NORTHEAST ACROSS IOWA THIS AFTERNOON...AND ACROSS WISCONSIN
TONIGHT WILL WEAKENING A BIT. SOUTHEAST WINDS WILL INCREASE ACROSS
LAKE MICHIGAN THIS MORNING AS THE SURFACE PRESSURE GRADIENT TIGHTENS
IN ADVANCE OF THIS LOW...WITH FORECAST SOUNDINGS INDICATING WIND
GUSTS TO 30 KTS ARE LIKELY. THE GRADIENT WILL THEN WEAKEN FROM THE
SOUTHWEST AS THE LOW MOVES INTO WISCONSIN TONIGHT...WITH WINDS
DECREASING FROM SOUTH TO NORTH AND VEERING TO THE SOUTH. THE LOW
WILL TRACK ACROSS NORTHERN LAKE MICHIGAN SUNDAY...WITH WINDS
EVENTUALLY VEERING TO THE WEST SUNDAY NIGHT AS THE CIRCULATION PULLS
OFF TO THE NORTHEAST AND CONTINUES TO WEAKEN. THE LOW WILL FILL
ACROSS SOUTHEAST ONTARIO MONDAY AND MONDAY NIGHT AS A NEW LOW
DEVELOPS ALONG THE ATLANTIC COAST.

WEAK HIGH PRESSURE RIDGING WILL SPREAD INTO THE WESTERN GREAT LAKES
TUESDAY...BEFORE A FAST MOVING LOW PRESSURE SYSTEM PASSES SOUTH OF
THE LAKES TUESDAY NIGHT. BRIEF HIGH PRESSURE RIDGING RETURNS
WEDNESDAY...BEFORE ANOTHER AREA OF DEEP LOW PRESSURE DEVELOPS OVER
THE SOUTH CENTRAL PLAINS WEDNESDAY NIGHT AND DEEPENS AS IT LIFTS
NORTHEAST TOWARD THE CENTRAL AND EASTERN LAKES THROUGH EARLY FRIDAY.
ALTHOUGH MODEL SOLUTIONS CONTINUE TO EVOLVE WITH THIS SYSTEM...THIS
DEEP LOW MAY RESULT IN VERY STRONG NORTHEAST TO NORTHWEST WINDS OVER
LAKE MICHIGAN THURSDAY NIGHT AND FRIDAY...WITH PERHAPS HIGH GALE OR
STORM FORCE WINDS POSSIBLE.

RATZER

&&

LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM SUNDAY.

&&

$$